A rare case of diffuse malignant peritoneal mesothelioma in a 71 year-old Malay man with no previous history of asbestos or radiation exposure is described. The clinical manifestation was a large abdominal mass. At laparotomy he was found to be in the advanced stage of the disease. The tumour was not resectable and patient was sent home. He gradually deteriorated and died three months after diagnosis was made. The magnetic resonance imaging (MRI) features of peritoneal mesothelioma which has not been previously reported are described.